Process for the manufacture of a plant substrate body

ABSTRACT

PEAT AND/OR SOIL IS DRIED TO A MAXIMUM WATER CONTENT OF 8-14%, BY WEIGHT, AND THE DRIED PEAT AND/OR SOIL IS MIXED WITH A LIQUID COMPOSITION OF REACTANTS FORMING AN ELASTIC POLYURETHANE FOAM. THE RESULTANT FOAM CONTAINS 20% TO 60%, BY WEIGHT, OF THE PEAT AND/OR SOIL AS AN EFFECTIVE PLANT GROWTH MEDIUM SUPPORTING THE ROOT STRUTURE OF A PLANT PLACED IN THE SUBSTRATE FOAM.

United States Patent 3,799,755 PROCESS FOR THE MANUFACTURE OF A PLANTSUBSTRATE BODY David Rack, Schwarzgrabenweg 17, Salzburg, Austria NoDrawing. Continuation-impart of abandouedapplication Ser. No. 216,225,Jan. 7, 1972. This application Apr. 25, 1973, Ser. No. 354,230 Claimspriority, application Austria, Jan. 12, 1971,

A 197/71 Int. Cl. C05f 11/02 US. Cl. 71--24 6 Claims ABSTRACT OF THEDISCLOSURE Peat and/or soil is dried to a maximum water content of8-14%, by weight, and the dried peat and/or soil is mixed with a liquidcomposition of reactants forming an elastic polyurethane foam. Theresultant foam contains to 60%, by weight, of the peat and/or soil as aneffective plant growth medium supporting the root structure of a plantplaced in the substrate foam.

, electrostatic charge accumulating on the foam.

In my prior application Ser. No. 41,355, filed May 28, 1970, I haveproposed a shape-retaining plant substrate comprising a clump of soiland/ or peat moss, and a polyurethane binder free of foaming orexpanding agent mixed with the soil and/or peat moss and binding theparticles thereof. Such a substrate can be used without a sheath orcasing without crumbling so that it may be readily transported without acontainer, and then used as a permanent substrate for supporting plantgrowth. On the other hand, the specific gravity of such a body is fairlyhigh.

It is an object of the invention toprovide aprocess for the manufactureof a plant substrate body which is not only simple and economical butwhich optimally promotes the growth of plants in a substrate bodywhichis uniform, elastic, porous and respiration-promoting, and through whichthe plant roots may grow well, having free water at their disposal. v

Standard soil and/or peat moss being materials suited for promotingplant growth, I have found that it is practically impossible to use themas plant growth promoting fillers in a polyurethane foam body unlesstheir normal water content of about 45%, by weight, has first beenreduced to about 8-14% by weight.

In the process of manufacturing a plant substrate body according to thepresent invention, a plant-growth promoting particulate materialselected from the group consisting of peat and standard soil is dried toreduce its water content to 8-14%, by weight, the dried material ismixed with a liquid composition of reactants including a blowing agentforming an elastic polyurethane foam, and the mixture is foamed by theblowing agent whereby the plant growth-promoting material is organicallybonded by the foam to form the substrate body, the amount of theparticulate material being such that the foam contains 20% to 60%,preferably about 40%, by weight, of the material.

If desired, fertilizers and/or other soil-improving mapolyurethanemixture.

3,799,755 Patented Mar. 26, 1974 terials compatible. with the liquidcomposition, i.e. which do not interfere with the foaming process, mayalso be incorporated in the mixture.

T he liquid composition may be wholly conventional and contain, forinstance, as A component a polyether having a high molecular weight(3000-4000) and a low OH number (25-65), a wetting agent having a lowmolecular Weight (50-500) anda high 0H number, a conventional foamstabilizer, and a conventional activator, and

as B component a commercially available di-for polyis10- cyanate, or amixture of different ,isocyanates. Liquid compositions of reactantsforming an elastic polyurethane foam are Well known.

'By way of example, a homogeneous composition is made from 100 parts byweight of the A component of a foamable polyurethane mixture, 35-40.parts by weight of peat and/or standard soil, and 0-15 parts by weightof another .plant substrate material, which may be organic or inorganic.This homogeneousmixtureis thoroughly mixed with 100 parts by. weight ofthe .B component of a foamable While the invention is not limitedthereto,,thefollow ingspecific examples illustrate the practice thereof,all parts being by weight. 1

EXAMPLE 1 I i Parts Polyether polyol .Desmophen 3800 100 Silicon-oil(additive SI) 1.5 .Amine activator Desmorapid CO 0.20 Stannous activatorDesmorapid SO 0.40 .Water -(as,blowing agent) 4 Peat having a Watercontent of 8% 40 Plant nutrients 10 Isocyanate fDesmodur T 5 0 EXAMPLE 2tainer of .suitable size constituting a mold for the substratebodyrAfter completingthe foaming reaction within a few minutes, a foambody of large volume and low specific gravity results. This body may becut into smaller shapes of any desired geometrical configuration toproduce plant substrate bodies ready for use.

The composition of the polyurethane foam is so selected that the endproduct has a very low specific gravity of about 15-60 kilograms percubic meter whereas its percentage of solids volume is very high. Thishas the advantage that such plant substrate bodies may be handled withgreat ease and convenience without crumbling. They constitute excellentpermanent plant growth media and have proved highly suitable for thecultivation and shipment of roses and other delicate ornamental shrubs.

This plant substrate body may also be used for growing lawns when it issubjected to a simple aftertreatment by the action of pressure and heat.In this aftertreatment, additional material, for instance a sheetingthrough which grass may grow, may be incorporated as a protectiveintermediate layer for controlling the moisture content of the substratebody, if this is required. By such an aftertreatment of the foam body,the specific gravity thereof is increased to about 50-100 kilograms persquare meter, and its carrying capacity is much increased while itsproperties promoting plant life, such as its respiration-promoting plantlife, such as its, respiration-promoting activity, Y 1

its excellent water-controlling capacity and the fact that plants growwell through the foam, are preserved. Such a substrate foam body enablesthe formation of a fine lawn, carpet even on a base of bare rock.Considerable areas of arable land may be reclaimed in this manner.

The heat and pressure treatment may be effected, for instance, by apress or pressure roll having a temperature of about 160 C. Thistreatment, lasting for instance about two minutes, will reduce thethickness of the foam plate or sheet from about 10 mm. to about 5 mm.

The rootstock' of plants implanted in substrate bodies made according tothe present invention remains firmly bonded therein throughout the lifethereof and ensures a sterile growth almost free of loss and in theabsence of weeds because any weed seeds which may be contained in thepeat or soil will bekilled by the exothermic reaction .heat generatedduring the foaming process.

The plant substrate body manufactured according to this invention may beused as a lawn mat for the fixation of subsoil on slopes which aresusceptible to elutriation and rock slides, e.g. on slopes at the sidesof highways.

While applicant does not wish to be bound by any theories, it is knownthat peat contains about 6% bound ,water' so that a peat having amoisture content of 6% contains no free water which could participate ina reaction. Peat having a water content of 8% theoretically :contains 2%free water which may react. Since water operates as a blowing agent inpolyurethane foam systems in certain stoichiometric amounts, the freewater in the peat or standard soil used in the present invention plays asignificant role in the formation of the substrate. Thus,

a the particulate material dried to the moisture content of theinvention'produces an amount of 2-8% free water,

advantageous for the use thereof as a plant growth me- "dium orsubstrate. Thus, the free water coming from the microporous peatparticles produces, during foaming, an

*open foam or sponge structure extending from the capillary surfacestructure of the peat particles and surrounding the same, transmittingthe strongly hydrophilic character of the peat to the surroundingpolyurethane foam at the interface between them. In this manner, thefree water coming from the peat during the foaming'reaction produces anopen-pored hydrophilic foamQThiswateradsorptive and water-deliveringcharacter of the foam 1 gives it its excellentquality as a plant growthmedium,

On the other hand, if the entire amount of water neeessary for theblowing reaction would be added from the outside, instead of coming fromthe peat or soil used in the mixture, i.e. if a peat were used which wasdried to a water content of 6% or less, a polyurethane foam would beformed around the peat particles which has closed pores and which is notin direct connection with the particles of peat or soil. An insulatinglayer of polyurethane foam would beformed at the interface of thecapillary peat surface and the surrounding foam, rather than the openpores of the foam entering into the capillaries. This would cause theresultant composite mass to lose the hydrophilic character of peat orsoil to a large extent.

I claim:

1. A process for the manufacture of a plant substrate body, whichcomprises foaming a mixture comprising a plant growth-promoting,particulate material selected from the group consisting of peat andstandard soil, the material having a water content reduced to about 8%to 14%, by Weight, and a liquid composition of reactants including ablowing agent forming an elastic polyurethane foam whereby the plantgrowth-promoting material is organically bonded by the foam to form thesubstrate body, the amount of the plant growth-promoting material beingsuch that the substrate contains from 20% to by weight, of the material.

2. The process of claim 1, wherein a fertilizer is incorporated into themixture.

3. The process of claim 1, wherein the liquid composition comprises an Acomponent including a polyether having a molecular Weight of 3000 to4000 and an OH number of 25-65 and a wetting agent having a lowmolecular weight of 50-500 and a high OH number, a foam stabilizer andan activator, and a B component including at least one isocyanate.

4. The process of claim 1, further comprising the step of subjecting theformed substrate body to heat and pressure to increase the specificgravity thereof.

5. The process of claim 1, wherein the mixture is foamed in contact witha perforate plastic material sheeting through which plants may grow.

6. The process of claim 1, wherein the substrate contains about 40%, byweight, of said plant growth-promoting material.

References Cited UNITED STATES PATENTS 3,417,171 12/1968 Eberle et al.7164 R 3,472,644 10/ 1969 Woodside et a1 711 2,192,939 3/1940 Slayter etal. 7164 G 3,077,700 2/ l963 Tukacs 7124 X 526,512 9/1894 Weber et a17164 A JOHN ADEE, Primary Examiner US. Cl. X.R. 7164 A, 64 G

